In marketing research, the term sampling refers to:

a$.$

Selecting representative individuals from a target population and treating their answers as typical of those in the target population.$$

b$.$

Allowing a subject to experience a new or updated product first$-$hand.

c$.$

Testing the effectiveness of a marketing campaign in a controlled setting.

d$.$

Testing members of all ages, genders, educational levels and income levels$$to guarantee reliable information.

e$.$

The collection of various secondary data through electronic means.